Vehicle differential assemblies are used to transmit driving torque from a vehicle engine to the wheels. A pinion gear is mounted to a vehicle driveshaft which is driven by the vehicle engine. The pinion gear is used to drive a ring gear in the differential assembly. Torque is transmitted from the ring and pinion, through the differential assembly, to a pair of transversely extending axles shafts. The torque supplied to the axles shafts is used to drive the vehicle wheels.
Traditionally, vehicle differential assemblies have been designed with a bolted joint configuration. The ring gear has a central bore that is located on the differential case by a pilot or press fit. The ring gear is attached to the differential case by a number of bolts or other fasteners. Additionally, dowels can be inserted through the ring gear and pressed into holes in the differential case to strengthen the bolted joint. It is difficult to accurately locate the holes for the fasteners and/or dowels such that the holes in the ring gear are aligned with the holes in the differential case.
Another difficulty with such a configuration is the strength and reliability of the bolted joint. During vehicle operation, vibrations and shock loads can loosen or weaken a bolted joint, which can eventually lead to failure of the joint.
Some differential assemblies also have two or more spider pinion gears located within the differential to accommodate situations where the axle shafts are turning at different speeds or in different directions. The spider pinion gears are supported on a single piece spider shaft having legs that correspond in number to the number of spider pinion gears. In other words, the spider shaft has a spider pinion gear supported on each of its legs.
Assembling a spider shaft that has more than two legs into the differential case requires the case to be made in two halves with a split along the centerline of the spider legs. Typically, these two halves are joined together by a number of bolts or other fasteners. In most instances, this is done using the same bolts that attach the ring gear to the differential case. This increases the difficulty in accurately locating the holes for the fasteners such that the holes in the ring gear are aligned with the holes in both halves of the differential case. Also, long bolts are required, which increases the cost for the differential assembly.
There are also various types of differential assemblies. There are standard differential assemblies and limited slip differential assemblies. A limited slip differential includes components for developing more traction at a wheel opposite from the wheel experiencing slip conditions. Different differential cases are required to accommodate the different components for the standard versus limited slip configurations. This proliferates the number of parts required for the differential assemblies.
Thus, it is desirable to have a differential assembly that can be used with either a standard or limited slip configuration and which does not require a bolted joint configuration so that the use of fasteners and dowels to mount the ring gear to the differential case can be eliminated. Also, it would be desirable to have a single piece differential case such that the fasteners used to connect the case halves could be eliminated. This would improve overall strength and reliability of the differential due to the elimination of the bolted joint and would also reduce cost and assembly time.